Sammendrag
This master thesis includes sampling of sediment cores from outside the river mouths of Three of the biggest rivers in Nord-Trøndelag; Steinkjerelva, Verdalselva and Stjørdalselva. The samples were decomposed and analysed by using the analysis instrument «Inductively Coupled Plasma-Mass Spectrometry» (ICP-MS), and the concentration of 65 different elements were examined. A selection of those elements was picked put for further studies based on assumptions about the elements that had a relevance to the possible local emission sources at the different localities. The purpose of the analysis was to study the time profiles (depth profiles) where the concentration of elements were studied at depth in the sediment cores. The various elements were then normalized against the aluminium concentration to identify possible anthropogenic inputs of the various elements. The result of this was normalization profiles, which was further studied together with time profiles.
The normalization profiles were imposed special weight and showed that the bulk of the anthropogenic input at all sites had occured in recent times, especially from the start of World
war II. The profiles also showed that the influence was different at the different locations. The correlations between aluminum and various elements were studied to uncover the elements that could be linked to anthropogenic input. All sediment samples were, in some varying degrees, affected by various anthropogenic and natural geochemical events, where the sediment sample outside Stjørdal was affected in the highest ratio by human activity. Examples of events that were related to human activity and that had changed the composition of the sediments; World War II, urban development, modernization of agriculture in the form of fertilizers and pesticides, mining and industrial activity. It was attempted to set sedimentation rates based on the dating of deviations in the normalization profiles for the elements that were related to specific anthropogenic and natural geochemical events. It proved to be variations in sedimentation rates both within the same sediment and between the various sediments. The degree of contamination of the elements arsenic, lead, cadmium, copper, chromium, mercury, nickel and zinc were compared against threshold values set by KLIF. This comparison showed that sediments in the whole were contaminated to a small, or no, degree VI by these elements, with the exception of copper, chromium and nickel in sediments outside the river mouths of Verdalselva and Stjørdalselva.
Vis fullstendig beskrivelse